Particulate filled coating composition of hydroxyl polyester cured with pyromellitic acid and a anhydride



United States Patent '0 PARTICULATE FILLED COATING CUB [POSITION OF HY DROXYL POLYESTER CURED WITH PYROMELLITIC ACID AND ANHYDRIDE Costel D. Denson, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Filed Aug. 14, 1961, Ser. No. 131,084 11 Claims. (Cl. 26040) This invention relates to resinous coating compositions. More particularly, the invention relates to resinous coating powders which are characterized by desirable flow characteristics and gel time which permit adequate coverage of articles to be coated in a minimum number of treatments and which are characterized by good corner coverage and bridging of discontinuous surfaces such as those of non-welded stators for electrodynamic machines, bundled wire structures as in wound stator end turns and the like.

The technique of coating heated articles, such as those of metal, by spraying or sprinkling powdered resin thereon or by dipping or tumbling them in a static powder bed or a suspended bed of resinous coating powders is well known and is readily adapted to articles of diverse shapes, particularly those having uniform or noninterrupted surfaces. However, in the case of articles having discontinuous surfaces such as non-welded stators for electrical machines having spaces of up to inch to inch between the laminations which form the surface of the stators, bundled wires or other non-uniform structures, it has generally been found that coating such articles by heating and coating by the above methods is often ineffective because the powder, after deposition and melting, does not flow sufficiently to coat the gaps or spread between the laminations and then gel in place at the proper time to provide adequate coverage. Attempts have been made to improve the flow characteristics and bridging ability of such powders by taking the obvious route of changing the filler characteristics of the compositions which influence flow characteristics. However, it was found that despite the manner in which the filler proportions and compositions were changed, the flow and gelling characteristics taken together were still inadequate satisfactorily to bridge discontinuous surfaces and at the same time provide adequate corner coverage, as well as over-all coverage in several treatments at the most. In other words, as the flow characteristics of the compositions were enhanced by changing the filler compositions and proportions to provide bridging ability, it was found that corner coverage and over-all coverage inevitably suffered. In some cases while adequate flow and coverage are attainable, the gel time of the resin is so long as to make the procedure uneconomical.

From the above, it will be quite obvious that there is a need for resinous coating compositions which have the ability at one and the same time to provide adequate coverage of extended surfaces as well as corners, and also to bridge discontinuous portions of the surface, such as are presented by spread laminations for dynamo-electric machines, bundled wire end turns, etc.

A principal object, therefore, of this invention is to provide resinous coating powders which will fulfill the above requirements, namely, to provide adequate coverage in a minimum number of treatments not only of surfaces but of corners and at one and the same time to provide such flow characteristics as will bridge and adequately coat discontinuities as above in the surface of the article to be coated with a reasonable gel time.

Briefly, the invention relates to coating powders comprising a polyester material, and filler material along with a critically balanced curing agent comprising pyromellitic 3,265,192 Patented Sept. 7, 1965 ice acid and pyromellitic dianhydride and pigment where desired.

After numerous experiments directed toward improving the flow characteristics of such resinous powder compositions by altering the fillers themselves and the proportions of fillers, all to no avail, it was unexpectedly found that a particular combination of curing agents, namely, pyromellitic acid and pyromellitic dianhydride, when used in certain specific proportions in conjunction with flow inducing fillers would so improve the flow and gelling characteristics .of the compositions as to provide not only adequate general coverage and corner coverage, but also to provide superior bridging ability. Specifically, it was found in a resinous composition comprising a polyester material and fillers to promote flow that if pyromellitic acid and pyromellitic anhydride were used in proportions ranging from 4 to l, the total amount of curing agent ranging from about 8 to 14 parts, by weight, per 100 parts of polyester material, a material was provided which would fulfill all of the above desirable characteristics. It was further found that if the weight ratio of pyromellitic acid to pyromellitic dianhydride was more than 4, the gel time of the resulting resinous composition was too long to attain curing in a reasonable time. Furthermore, excess pyromellitic acid lowers the bonding strength. On the other hand, it was found that if the weight ratio of the pyromellitic acid and pyromellitic dianhydride was less than about 1, the gel time of the resulting resinous compositions was so short, of the order of about 3 minutes, that proper flow to achieve the above purposes was not provided.

The polyester materials used in conjunction with'this invention are described in detail in Patent No. 2,936,296, assigned to the same assignee as the present invention and included herein by reference. Briefly, the polyester resin comprises (a) from about 25 to 56 equivalent percent, preferably from 36 to 50 equivalent percent, of isophthalic or terephthalic acid or a lower dialkyl ester of a member selected from the class consisting of isophthalic acid and terephthalic acid and mixtures therof, (b) from about 15 to 46 equivalent percent, and preferably from 25 to 40 equivalent percent, of ethylene glycol, and (c) from about 13 to 44 equivalent percent, and preferably from 20 to 32 equivalent percent, of a saturated aliphatic polyhydric alcohol having at least three hydroxyl groups. Typical of the isophthalic and terephthalic acid esters which may be used are those dialkyl esters containing from 1 to 8, and preferably from 1 to 4, carbon atoms including the dimethyl, diethyl, dipropyl, dibutyl, etc. esters. The terms polyhydric alcohol and saturated aliphatic polyhydric alcohol having at least three hydroxyl groups include both polyhydric alcohols in which the hydroxyl groups are connected by a plurality of carbon to carbon linkages, as well as other alcohols having three or more hydroxyl groups, such as glycerin, 1,1,l-trimethylol ethane, sorbitol, mannitol, diglycerol, trimethylol propanes, dipentaerythritol, etc. The ethylene glycol can be replaced in whole or in part by other diols including but not limited to butane diol, neopentyl diol, pentane diol, etc. which will occur to those skilled in the art. The term diol is herein taken to mean such diols as well as mixtures thereof.

The term equivalent percent is employed in its usual sense herein, it being the number of equivalents of the reactant divided by the total number of equivalents of all reactants times one hundred. The number of equiv- 4 alents of a reactant is the number of moles of the reactant multiplied by the number of functional groups Typical of the polyesters along with the others described in the above cited patent which can be used and is preferred in the practice of the invention, is one prepared from the following ingredients:

Dimethyl terephthalate 46 equiv. percent (3 moles) Ethylene glycol 31 equiv. percent (2 moles) Glycerin (95%) 23 equiv. percent (1 mole) The above materials are added along with xylene or a similar solvent, to prevent sublimation of lower dialkyl esters of the acids, to a three-necked flask having a thermometer, stirrer and a Vigreux column with a Dean and Stark trap and funnel on the column. A nitrogen blanket is also provided for the system. The system is heated for about 30 minutes, during which time the pot temperature rises to about 130 C. and the water and xylene az-eotropically distill fromthe system. Then about 0.03 percent by weight of lead acetate as an alcoholysis catalyst based on the weight of the dimethyl terephthalate is added and heating continued for about three and one-half hours to a final temperature of about 240 C. It will be realized, of course, that other alcoholysis catalysts can be used such as lead oxides, zinc oxide, cadmium acetate, cuprous acetate, zinc acetate, etc.

The fillers employed in connection with this invention are well known and are characterized by the fact that they have a surface to volume ratio expressed in square meters per cubic centimeter of from about 100 to 500. Lesser amounts and as little as several or even less parts of the finer fillers or those of the larger surface to volume ratios can be used with each 100 parts by weight of polyester resin while up to 100 parts of the coarser fillers are usually indicated. Among the fillers which have been found useful in connection with this invention are fumed silicas, such as Cab-O-Sil made by the Godfrey L. Cabot Company, which have a surface to volume ratio of about 420 square meters per cubic centimeter. Also useful are the Micro-Cel materials, which are silicates prepared by the Johns-Manville Company. Micro-Cel C has a similar surface to volume ratio of 394; Micro-Cel E has a similar ratio of 232 and Micro-Cel T-35 has a like ratio of 121. Also useful are the clay-like materials, such as Attagel 20, of Minerals and Chemicals Corporation of America which has a ratio of 495 square meters per cubic centimeter. Other suitable fillers will occur to those skilled in the art.

The pyromellitic acid and .pyromellitic dianhydride used in the present invention are of the usual commercial grades.

Generally speaking, for each 100 parts by weight of polyester material there are used from up to about 90 parts of finely divided filler having the above characteristics and from about 8 to 14 parts of a curing or crosslinking agent comprising pyromellitic acid and pyromellitic dianhydride such that the weight proportions of acid to dianhydride ranges from 4 to 1 and most preferably 65/35. When pigmenting is desired, up to about 10 parts of a material such as titanium dioxide or other suitable pigment are used to obtain the'requisite color. If more than 14 parts of cross-linking agent are used, the excess material tends to make the coatings moisture sensitive. On the other hand, if less than about 8 parts are used, the coatings have poor solvent resistance and a lowered cut-through temperature.

In preparing the resinous compositions of the present invention, a dough mixer is typically employed into which the polyester material is slowly added until it has all melted and reached a temperature of from about 130 C. to 138 C., the pigment, if any being added after this temperature range is reached and with the machine still in operation. About minutes are allowed for incorporation of the pigment. Next, with the mixer stopped, the finely divided filler is added in convenient proportions and thoroughly mixed between additions, care being taken so that the filler does not overflow from the dough mixer. When the last of the finely divided filler is thoroughly dispersed from a visual standpoint, the composition is further mixed up to several hours. Next and while the mixer is still in operation, the cross-linking mixture is added in convenient portions over a period of between 4 to 6 minutes. The cross-linking agent is prepared simply by measuring out the prescribed amounts of pyromellitic acid to which is add-ed the proper amount of pyromellitic dianhydride, which latter is thoroughly dispersed throughout the acid and sealed against moisture until actual mixing with the polyester. After the preparation of the resin-filler-curing agent mixture has been completed, the material is dumped from the mixer and allowed to cool to room temperature and ground to a size as required by the particular coating procedure to be used. The primary consideration in the preparation of the materials is through admixture and blending. Equivalent methods of preparation will occur to those skilled in the art.

In order to provide a still more precise control of flow characteristics and in particular the ability of the material to cover sharp corners, it has been found expedient in some cases to add only a portion of the finely divided filler to the hot blended resin, the remainder of such filler being later cold-blended with the ground resin composition or, alternatively, cold-blending all of the finely divided filler or even hot-blending all of the filler. Generally, hot-blending is employed when a homogeneous coat is desired and larger amounts of filler are used whereas with lower percentages, some can also be cold blended.

If a portion of the filler is to be cold-blended, this is done preferably just before use, the additional amount of finely divided filler to be cold-blended being added in convenient amounts in a usual blending machine.

In addition to preparing the present materials in a machine such as a dough mixer which has a shearing and smearing action, it has been found convenient to prepare the compositions also in a rubber mill type of machine which is also characterized by the same type of shearing and smearing mixing action. In this case, the polyester is added to the nip of the rolls and the various filler and curing catalyst additions made in convenient fashion with the final resinous composition sheeting off the rolls like rubber.

It is also feasible to use the spray drying process for preparing the present materials, solutions of polyester and suspensions of the fillers and curing catalysts being mixed together and spray dried in manners which are well known to those skilled in the art.

The gel time of the present materials is of the order of five minutes. The materials after coating can be cured with heat in the well-known manner such hardening being of a time-temperature nature. Typically, the coating is cured for forty-five minutes at 220 C. to 225 C. It will be realized that a step cure can be used, for example, heating at 180 C. for one-half hour and then 220 C. for a like period. The curing cycle is of a timetemperature nature and other useful cycles will occure to those skilled in the art.

The following examples illustrate the practice of the invention, it being realized that they are not to be taken as limited in any way:

Example 1 There were added to a dough mixture with stirring parts by weight of the above preferred polyester, the material being added slowly until it had melted and reached a temperature of from about C. to 138 C. Ten parts of titanium dioxide pigment were added at this point with the machine in operation, five minutes being allowed for incorporation of the pigment. Next, with the dough mixture stopped, a total of 11 parts of fumed. silica or Cab-O-Sil were added in convenient proportionswith thorough mixing between additions. When the fumed silica had all been dispersed, the material was further mixed for about two hours. Then, with the mixer still in operation, parts per 100 parts of resin of a mixture of pyromellitic acid and pyromellitic dianhydride were added, the weight proportion of acid to dianhydride being 6.5 to 3.5. The cross-linking mixture was added over a period of 5 minutes. The material was then dumped from the mixer, allowed to cool and ground to a size of about 80 mesh. When this material was coated from a powdered suspension on a test piece having a right angle with a recessed fillet having an opening of about inch, thorough coverage of both the con tinuous parts of the test piece, as well as complete bridging of the fillet and good corner coverage, was obtained in the heat cured article.

Example 2 Example 1 was repeated except that 12 parts per 100 parts of fumed silica of the above type were used. Once again, good bridging and general and corner coverage, as well as thorough coverage of continuous surfaces, were obtained.

Example 3 Example 1 was repeated except that 14 parts by weight of fumed silicate per 100 parts of the polyester were used. Results were similar for those of Examples 1 and 2.

Example 4 Example 1 was repeated using 6 parts of fumed silica filler. After the complete coating powder had been made and pulverized, an additional 0.5 part of fumed silica was cold blended thoroughly with the coating mixture. This material when coated on a test piece as above in a suspended bed of powder coated on corners adequately bridged discontinuities and in general provided a good coating on continuous surfaces as well.

Example 5 Example 1 was repeated using 3 parts of titanium dioxide and a mixture of 3.5 parts pyromellitic dianhydride and 6.5 parts pyromellitic acid per 100 parts of by weight the above preferred polyester. Fumed silica in the amount of 2.5 parts was hot-blended while about 0.8 part was cold blended. The material coated very well from a suspension in the manner of the material of Example 1.

Example 6 Example 5 was repeated using 1 part of fumed silica cold-blended to produce a good coating material.

Example 7 Example 5 was repeated using 2.5 parts of fumed silica hot-blended and 1 part fumed silica cold-blended. Again, a good coating material resulted.

Example 8 Example 1 was repeated using 3 parts of titanium dioxide and 2.5 parts of fumed silica per 100 parts of preferred polester. The curing agent was 10 parts of pyromellitic acid. While this provided a smooth flowing coating material the gel time of about 30 minutes was far too long.

Example 9 Example 8 was repeated except that 10 parts of 60% by weight pyromellitic dianhydride and 40% pyromellitic acid were used. This material while flowing and covering very well, gelled in about two minutes after addition of the curing agent which is too short a time for production work.

Example 10 Example 5 was repeated using 10 parts of pyromellitic dianhydride. This material gelled too quickly to form a good coating composition.

6 Example 11 Example 1 was repeated except that in lieu of the fumed silica, a silicate known as Micro-Cel C having surface to volume ratio of 394 square meters per cubic centimeter was used. Once again, when test pieces were coated from a suspended bed of this material, good coatings as above were secured.

Example 12 Example 11 was repeated except that 13 parts per 100 of the silicate material of that example were used, once again, with salutary results.

Example 13 Example 11 was repeated using 15 parts of the Micro- Cel silicate material of Example 11. Test pieces coated from a suspended bed of this material were thoroughly coated including corners as well as bridging of discontinuities.

Example 14 Example 1 was repeated except that in lieu of the fumed silica 11 parts of a silicate known as Micro-Cel E having a surface to volume ratio of 232 square meters per cubic centimeter was used. This material provided a coating composition which thoroughly coated heated test pieces submerged therein, including corners, continuous surfaces, as well as discontinuous surfaces.

Example 15 Example 14 was repeated except that 15 parts of the finely divided silicate were used in lieu of 11 parts. Once again, a good coating composition was obtained which satisfactorily coated test pieces as above.

Example 16 Example 14 was repeated except that 20 parts of the finely divided silicate were used to produce a coating composition which satisfactorily coated heated test pieces as above.

Example 17 Example 1 was repeated except that 70 parts of a finely divided silicate known as Micro-Cel T-35 having a surface to volume ratio of 121 square meters per cubic centimeter were used. This coating composition when used to coat heated test pieces dipped in a suspended body of the composition thoroughly coated continuous surfaces, corners and discontinuous surfaces as above.

Example 18 Example 17 was repeated except that 75 parts of the finely divided silicate were used, once again, producing a good coating composition.

Example 19 Example 17 was repeated except that parts of the finely divided silicate of Example 17 were used to produce a coating composition having the same superior coating qualities.

Example 20 Example 1 was repeated except that a clay-like silicate material Attagel 20 having a surface to volume ratio of 495 square meters per cubic centimeter was used in amounts of 19 parts per parts of the above preferred polyester resin. The coating composition when used to coat heated test pieces dipped in a suspension thereof adequately covered the continuous surfaces of the test piece as well as corners and discontinuities therein.

Example 21 Example 20 was repeated except that 25 parts of the Attagel material were used, once again, producing a good coating composition.

7 Example 22 Example 20 was repeated in all respects except that 29 parts of the Attagel were used to produce a good coating composition.

From the above, it will be seen that there are produced by the present invention coating compositions which are characterized by ready application to production processes. They can be used to coat continuous surfaces, at the same time adequately covering corners of the objects to be coated as Well as discontinuities in the structure to be coated. The coating compositions are characterized by good electrical insulating qualities as well as resistance to solvents and other chemical action. They are tough and resistant to mechanical shock such as is encountered in assembling electrical machinery, the parts of which are so coated. They are useful in general where any struc tural part or article is desired to be coated with a resinous material.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A resinous composition comprising (1) 100 parts, by weight, of a composition comprising the curable heat reaction product of (a) from about 25 to 56 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid and mixtures thereof, (b) from about 15 to 46 equivalent percent of aliphatic diol, and (c) from 13 to 44 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) an amount up to about 90 parts, by weight, of a finely divided filler having a surface to volume ratio ranging from about 100 to 500 square meters per cubic centimeter, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic dianhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

2. A resinous composition comprising 100 parts, by weight, of (I) a composition comprising the curable heat reaction product of (a) 46 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid, and mixtures thereof, (b) 31 equivalent percent of aliphatic diol, and (c) 23 equivalent percent of saturated aliphatic polyhydric alcohol having at least thre hydroxyl groups, (II) an amount up to about 90 parts, by weight, of a finely divided filler having a surface to volume ratio ranging from about 100 to 500 square meters per cubic centimeter, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic anhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

3. A resinous composition comprising (I) 100 parts, by weight, of a composition comprising the curable heat reaction product of (a) from about 25 to 56 equivalent percent of a material selected from the class consisting of isophthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid and mixtures thereof, (b) from about 15 to 46 equivalent percent of aliphatic diol, and (c) from 13 to 44 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) an amount up to about 90 parts, by weight, of a finely divided filler, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic dianhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

4. A resinous composition comprising 100 parts, by weight, of (I) a composition comprising the curable heat reaction product of (a) 46 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid, and mixtures thereof, (b) 31 equivalent percent of aliphatic diol, and (c) 23 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) an amount up to about parts, by weight, of a finely divided filler, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic anhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

5. A resinous composition comprising (I) parts, by weight, of a composition comprising the curable heat reaction product of (a) from about 25 to 56 equivalent percent of dimethyl terephthalate, (b) from about 15 to 46 equivalent percent of ethylene glycol, and (c) from 13 to 44 equivalent percent of glycerine, (II) an amount up to about 90 parts, by weight, of a finely divided filler, and (III) from 8 to 14 parts, by weight, of a mixture of pyro mellitic acid and pyromellitic dianhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to l.

6. A resinous composition comprising 100 parts, by weight, of (I) a composition comprising the curable heat reaction product of (a) 46 equivalent percent of dimethyl terephthalate, (b) 31 equivalent percent of ethylene glycol and (c) 23 equivalent percent of glycerine, (II) an amount up to about 90 parts, by weight, of a finely divided filler, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic anhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

7. A resinous composition comprising (I) 100 parts, by weight, of a composition comprising the curable heat reaction product of (a) 25 to 56 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid, and mixtures thereof, (b) 15 to 46 equivalent percent of aliphatic diol, and (c) 13 to 44 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) about 3 parts, by weight, of fumed silica, (III) 10 parts, by weight, of a mixture of 3.5 parts, by weight, of pyromellitic dianhydride and 6.5 parts, by weight, of pyromellitic acid and (IV) 3 parts, by weight, of pigment.

8. A resinous composition comprising (I) 100 parts by weight of a composition comprising the curable heat reaction product of (a) 46 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid, and mixtures thereof, (b) 31 equivalent percent of aliphatic diol, and (c) 23 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) about 3 parts, by weight, of fumed silica, (III) 10 parts, by weight, of a mixture of 3.5 parts, by weight, of pyromellitic dianhydride and 6.5 parts, by weight, of pyromellitic acid, and (IV) 3 parts, by weight, of pigment.

9. A resinous composition comprising (I) 100 parts, by weight, of a composition comprising the curable heat reaction product of (a) from about 25 to 56 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid and mixtures thereof, (b) from about 15 to 46 equivalent percent of aliphatic diol, and (c) from 13 to 44 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) an amount up to about 15 parts, by weight, of fumed silica, and (III) from 8 to 14 parts, by weight, of a mixture of pyromellitic acid and pyromellitic dianhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

10. A resinous composition comprising (I) 100 parts, by weight, of a composition comprising the curable heat reaction product of (a) from about 46 equivalent percent of a material selected from the class consisting of isophthalic acid, terephthalic acid, lower dialkyl ester of isophthalic acid, lower dialkyl ester of terephthalic acid and mixtures thereof, (b) from about 31 equivalent percent of aliphatic diol and (c) 23 equivalent percent of saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, (II) an amount to about 15 parts, by weight, of fumed silica, and (III) from 8 to 14 parts, by Weight, of a mixture of pyromellitic acid and pyromellitic dianhydride in which the ratio of pyromellitic acid to pyromellitic dianhydride ranges from about 4 to 1.

11. A resinous composition comprising (I) 100 parts of a composition comprising the curable heat reaction 10 product of (a) 46 equivalent percent dimethyl terephthalate, (b) 31 equivalent percent ethylene glycol and (c) 23 equivalent percent glycerine, (II) about 3 parts, by weight, of fumed silica, (III) 10 parts, by weight, of a mixture of 3.5 parts, by weight, of pyromellitic dianhydride and 6.5 parts, by weight, of pyromellitic acid, and (IV) 3 parts, by weight, of titanium dioxide.

References Cited by the Examiner UNITED STATES PATENTS 5/60 Precopio et a1 26022 XR OTHER REFERENCES Trimellitic Anhydride, Amoco Chem. Corp., 1958.

MORRIS LIEBMAN, Primary Examiner.

MILTON STERMAN, Examiner. 

1. A RESINOUS COMPOSITION COMPRISING (I) 100 PARTS, BY WEIGHT, OF A COMPOSITION COMPRISING THE CURABLE HEAT REACTION PRODUCT OF (A) FROM ABOUT 25 TO 56 EQUIVALENT PERCENT OF A MATERIAL SELECTED FROM THE CLASS CONSISTING OF ISOPHTHALIC ACID, TEREPHTHALIC ACID, LOWER DIALKYL ESTER OF ISOPHTHALIC ACID, LOWER DIALKYL ESTER OF TEREPHTHALIC ACID AND MIXTURES THEREOF, (B) FROM ABOUT 15 TO 46 EQUIVALENT PERCENT OF ALIPHATIC DIOL, AND (C) FROM 13 TO 44 EQUIVALENT PERCENT OF SATURATED ALIPHATIC POLYHYDRIC ALCOHOL HAVING AT LEAST THREE HYDROXYL GROUPS, (II) AN AMOUNT UP TO ABOUT 90 PARTS, BY WEIGHT, OF A FINELY DIVIDED FILLER HAVING A SURFACE TO VOLUME RATI RANGING FROM ABOUT 100 TO 500 SQUARE METERS PER CUBIC CENTIMETER, AND (III) FROM 8 TO 14 PARTS, BY WEIGHT, OF A MIXTURE OF PYROMELLITIC, ACID AND PYROMELLITIC DIANHYDRIDE IN WHICH THE RATIO OF PYROMELLITIC ACID TO PYROMELLITIC DIANHYDRIDE RANGES FROM ABOUT 4 TO
 1. 